2. amps-preamps
  3. 142214-112817

Am I asking too much?

I've spent the last three days chasing a ground loop/hiss issue.  I have unplugged and replugged every combination possible, have tried different type of grounds to phono stage, tried different phono stages, different lines into the amp, different turntables and still when I crank the volume with nothing playing, have this hiss.  At lower volumes I don't hear it, but if I turn it up, it's there.  I probably would never listen that loud, but still worry that at base levels the sound is compromised.  I've had this system connected for a month and don't know if the hiss was always there, or if, when I had to rearrange and reconnect due to Christmas and the wife factor, something changed.

My system is a Line Magnetic LM216IA tube amp, a Heed phono stage, a Rega Planar 3 TT (which doesn't have a ground wire) which plays to Audio Physic bookshelves and a JL Audio e110 sub. One of my biggest concerns has been the lack of ground with the Planar 3.

My system is plugged into a Torus Power Conditioner, so I thing I have that base covered into a dedicated line.  With all these electrical precautions am I expecting too much asking for a black speaker background?

Will be interested to hear similar ground loop stories or thoughts on whether there are other issues that I haven't considered.

udog
cakyol's avatar
cakyol
940 posts
 
Use a Jensen audio isolator transformer for HUM ONLY: http://www.jensen-transformers.com/transformers/

Hiss is the noise floor of the electronic components.  U cannot get rid of it unless u have tone controls are you are ok with turning the treble down.  And that will help only so much.


udog OP
32 posts
 
Thanks for all the comments and help.  With your assistance and more experimentation, it is pretty clear that what I have is hiss and not a hum.  I guess it is an amp related problem caused by tubes. Not sure where to go from here or whether it is something I have had and never noticed or if it can be rectified.
gregdude
222 posts
 
Line magnetic makes a god product. What is the condition of the tubes? NOS replacement tubes may be in your future.... try some of the cv 4004 version of the 12ax7 or any of the U.S. made 12ax7's. JJ makes a good kt88 and I enjoyed the new tungsols too. 
tastyfreeze's avatar
tastyfreeze
135 posts
 
udog, I feel for you as I have chased this scnerio.  
smrex13
645 posts
 
My questions would be: how loud is the hiss? How far do you have to turn up the volume control before you start hearing it? Is it audible in the range that you use to listen to music? In my experience a phono stage will almost always generate significant hiss if you turn your system's volume control all the way up.

I read about people who can only hear a faint hiss if they put their ear up to the tweeter when the volume pot is wide open. I can’t even imagine how that happens. With every combo of gear I’ve had in my system (tubes, SS, pre/power, integrated, power conditioner, no power conditioner), turning the volume all the way up generates 60-85db of hiss (measured at the tweeter), easily audible from the next room. In most cases with gear I’ve tried, the hiss doesn’t become audible until the volume control is at about 50% (varies by component, of course), which is much louder than I would ever listen.

As long as the hiss is below the level at which you listen, I don’t think you have anything to worry about. You’ll drive yourself crazy (and spend a lot of money) trying to stamp out that last bit of hiss.

Good luck!
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